It is known that an orthogonal frequency division multiplexing (OFDM) scheme has a very high peak-to-average power ratio (PAPR) of a transmission signal. Since transmission signals with a high PAPR cause distortion due to power amplifiers, reducing the PAPR is an important research topic and numerous PAPR reduction methods have been devised. Among them, a partial transmit sequence (PTS) has a feature of not causing distortion of the transmission signal and thus, it is regarded as a favorable PAPR reduction method. Here, the PTS is a method of dividing an OFDM subcarrier into a plurality of blocks and performing a phase rotation on transmission signals corresponding to the respective blocks to reduce the PAPR.
Incidentally, a transmission device that transmits a transmission signal on which the PTS has been performed needs to notify a reception device that receives this transmission signal of a phase rotation amount which is the amount of a phase rotation performed on the transmission signal. However, if the environment of a channel conveying the transmission signal between the transmission device and the reception device is poor, the transmission device is not able to notify the reception device of the phase rotation amount in some cases. In this case, it becomes difficult for the reception device to demodulate the received transmission signal.